Liquid fuels derived from biomass have long been studied as alternatives to fossil fuels. While the net energy yield and greenhouse gas reduction achieved with current biofuel conversion processes remains controversial, biofuels produced from cellulosic feedstocks hold great potential as a source of renewable, carbon neutral liquid fuel. Current conversion processes rely heavily on enzymatic conversion of cellulose to glucose for fermentation to ethanol or other fuels. Production of these enzymes from filamentous fungi, or purchase from another party, represents a major cost in the total conversion process. Efforts to reduce this cost have been a major focus of recent public and private research on biofuel production.
The greatest advances in cellulase production to date have been achieved by iterative, random mutagenesis of filamentous fungi. While this strategy has reduced the cost of enzyme production substantially, the resultant strains have hundreds of mutations. It is not clear which mutations have given rise to the desired increase in yield and which mutations are irrelevant or impair cellulase production. Without a fundamental understanding of how particular mutations improve cellulase yield, it will be difficult to further engineer industrial strains or transfer increased productivity to other strains of interest. A more systematic understanding of the biological process involved in cellulase production by filamentous fungi, and related compositions and methods, are needed.